Heating apparatus and radiation relay therefor



June 3, 1952 s. H. LEDIN HEATING APPARATUS AND RADIATION RELAY THEREFORFiled April 20, 1949 v m Wm WM A mm 3% MUM/1!! H I 6 H A? 7 PatentedJune 3, 1952 HEATING AFPARATUS ND RAnlArioN RELAY THEREFOR Sven HaraldLedin, Malarhojden, Sweden Application April 20, 1949, Serial No. 88,596In Sweden April 24, 1948 12 Claims. 1

The present invention relates to radiation relays and their applicationas temperature indicators praticularly for heating apparatus, such as"furnaces, stoves, oil or gas heated boilers etc., but, may be, also forfire alarm.

It is an object of the invention to provide a cheap and relativelyrobust relay or indicator which is comparatively simple in construction,and a particular object is to provide such a relay or indicator which isat least practically unresponsive or controllably responsive tovariations in the temperature of the surroundings. One specific objectis to provide a cheap and reliable safety relay for oil and gas heatersfor cutting oft the supply of oil or gas and, if desired, of pressureair in case, for some reason, the flame should become extinguished andthe fireplace be loaded with oil or gas which might cause explosion orother damage.

To obtain these and other valuable objects which will be apparent as thedescription proceeds or otherwise well understood by those skilled inthe art, the relay comprises a contact lever carried by at least twoexpansion members arranged so that by their thermal expansion they willboth displace the lever in the same direction, one of said members beingadapted to receive radiation and thereby expand relative to the othermember and thus tilt said lever to cause a contact member on said leverto engage a stationary contact member and close an electric currentcircuit. Most materials having a positive coefficient of thermalexpansion the following description will refer to such materials but itis to be understood that the invention as claimed comprises also the useof expansion members having a negative coefficient.

Theinvention will now be described more in detail with reference to theaccompanying drawing illustrating some embodiments to which it is,however, not restricted.

In the drawing:

Fig. 1 shows an assembled relay containing an aera in implement andFigs. 2 and 3 are semi-diagrammatic illustratiqns of two difierentembodiments of the radiation relay alternative to that shown inassembled relay of Fig. 1.

Fig. 4 shows a preferred mode of attaching the relay to an oil heatedfurnace.

Fig. 5 shows a modified construction of a detail of the structureillustrated in Fig. 1.

' In Figfl the thermal expansion members consist of metallic bands I and2 which may be, for instance, 5 to 10 centimeters in length, 3 to 6millimeters wide and 0.05 to 0.2 millimeter thick.

They are secured in a spaced relationship, for instance by soldering, toa support 3 which is in turn attached to the holder 4 by means ofelectrically insulating plates 8 bolted to support 3 and holder 4 byscrews 5 and 6, respectively, and under the intermediation of aninsulating pack ing 1. Packing 1 may be removed and replaced by aninsulating air-gap. At their remote end the bands I and 2 are fixed tothe contact lever is, for instance, by being double folded at the ends,preferably over a small pin and having such ends inserted intotransversal outwardly tapering grooves H in the lever. The lever [0 hasan arm l2 extending parallelly to, preferably along the bands 6 and 2.'At its end the arm carries a contact point I3 opposite to a contactdisc M mounted at the end of the screw I5 axially adjustable in a borein holder 4. The point 13 should be at a distance from the attachmentpoint of band 2 in lever ID at least as big as the distance between theattachment points of bands l and 2 in the lever. The lever I0 is, in theembodiment illustrated, suspended in holder 4 and will be kept stretchedby a spring l6 secured to holder 4 and by the stud H to the lever ill.The electric circuit to be controlled by the relay is admitted throughthe wires H3 and E9 connected to screws 5 and 6.

When in use the relay will be so located as to expose band i to theradiation from the heat source to be observed, for instance the flame ofa burner or an electric resistance. To promote the thermal expansioneffect of the radiation the band I may be more or less black. Band 2, onthe other hand, may be protected more or less from such radiation, forinstance, by being screened off by band I. To reduce its radiationabsorbing capacity it should be made bright or shiny, preferably bychromium, platinum and/or rhodium plating it which will render it apermanent right coating. Upon radiation the thermal expansion of band Iwill thus be in excess of that of band 2. As the radiation impingingupon the band i or bands and 2, respectively, increases, the differencein thermal expansion of the bands will become greater and contact point53 will thereby approach contact disc I4, and at a given amount ofradiation the contact members will contact one another and close theelectric circuit, which is supposed to permit the normal supply of heatsource (oil, gas, electric current etc.) or give a signal or the like,as the case may be. As long as the. heater is running normally theradiation from its heat source will be sufficient to maintain thecontact, but should the flame become extinguished or any other heatsource used become void, the band I will recontract and the contactI3-I4 be broken, which, in turn, will obstruct the supply of heat sourceor give a signal, as the case may be.

In order to become sensitive and quick-answering to the radiation theband I should have a small cross-section so as to reduce the mass thathas to be heated by the radiation, and, if desired, be heat insulatedfrom the other parts so as to avoid loss of heat by conduction. For thesame object it should be made of a material having a high coefficient ofthermal expansion, such as zink, aluminium, copper or brass.

Bands I and 2 should also be small in crosssection and preferably bepractically equal in that respect for the reason that either band shallrespond equally to variations in the surrounding temperature. For thesame reason the heat capacities and coefficients of thermal expansion ofthem should not differ very much but rather be equal.

If the bands I and 2 are equal in length and made of the same orequivalent material their thermal expansion on account of variations inthe temperature of the surroundings will be equal and merely result inparallel displacement of the lever I0, and if the contact surface of thecontact disc I4 is parallel to such displacement no alteration in thespacing of the contact members will occur. Variations of the surroundingtemperature will thus have no influence on the Working of the relay.Much the more so if the arm I2 is placed alongside of the bands and madeof the same or equivalent material since in that case the upwardelongation of the bands will be compensated by a downward elongation ofarm I2.

On the other hand, by suitably varying the dimensions of and/or thematerials chosen for the bands, the present instrument may be made to beinfluenced in a controllable way by the surrounding temperature or, as acorollary, may the variation of some of the factors be compensated bythe variation of others. Thus, increase in length and coefficient ofthermal expansion will promote the expansion as will, at leastmomentarily, increase in surface of a given volume, whereas increase incross-sectional area of a given volume and heat capacity will, at leastmomentarily, retard expansion. The present relay usually being adaptedfor rapid response, even said factors having only a momentary influencewill obviously be useful. If, for example, band 2 is made shorter thanband I or is substituted to a greater or smaller extent by a materialhaving a lower coefficient of thermal expansion relative to band I, anincrease in the temperature of the surroundings will turn lever I0 sothat contact point I3 will approach contact disc I4, and vice versa. Iftherefore, for instance, band I is made of plain steel and band 2 ofaluminium, the lever will obtain no rotary movement provided band 2 ismade about half as long as band I and is supported in a practicallyinexpansible piece of wood.

If desired, such temperature response may instead be compensated more orless by setting contact disc I4 at an adequate angle to the lengthdirection of the bands, as shown in Fig. 5.

According to one embodiment of the invention the band I and/or band 2may be thick enough or provided with reinforcing ribs or grooves. Thesuspension of lever ID in holder 4 may then be dispensed with, but forthe reasons just described such instrument will usually be lesssensitive due to the relatively great masses.

The embodiment shown in Fig. 2 is near related to that shown in Fig. 1but in order to make the structure more compact and less bulky the bandsI and 2 are in a helical or in a combined helical and screw arrangement.They are secured to a central support 3 and carry at their ends thelever I0 which is also fixed to a spring I6. The lever has an arm I2which is in this case curved in accordance with the helix. At the end ofthe arm is a contact point I3 cooperating with a stationary contactsegment I4 which is curved similarly to the arm and adjustable by meansof a setting screw I5 secured to a holder 4. In principle, this deviceoperates as that of Fig. 1.

Fig. 3 illustrates an embodiment having two diaphragms 2| and 22 fixedin annular supports 23 and 24, respectively, in such a manner as tobulge to the one sidei The diaphragms are secured to a contact lever 25inserted between the diaphragms through the intermediation of connectingpieces 26 and 21, respectively, fixed at about the middle of thediaphragms and at places on the lever spaced from one another to form amoment arm. Due to their bulging state the diaphragms will move axiallyof the annular supports when expanding thermally. In agreement therewiththe lever 25 has an arm 28 extending substantially in parallel with suchaxial movement and carrying at its extreme end a contact point I3cooperating, as in the embodiment already described in connection withFig. 1, with a stationary contact disc I4 fitted to the end of anadjustment screw I5 threaded in an insulated bushing 29 in a holder 4.

Although subject to such variations as explained above in connectionwith Fig. 1, the diaphragms 2I and 22 are now supposed to be equalenough to react identically upon variations in the temperature of thesurroundings. Therefore such temperature variations will merely resultin a translatory movement of lever 25 and the distance of contact pointl3 from contact disc I4 will remain constant. If on the other handradiation, indicated by the arrows, falls upon diaphragm 2I the thermalexpansion of that diaphragm will be excessive of that of diaphragm 22resulting in a turning of lever 25 and an approach of contact point I3to contact disc I4, until upon sufiicient radiation these contactmembers will finally contact.

As illustrated in Fig. 1 the relay is preferably protected by a housing3| having an opening 32 for admitting the radiation to the radiationabsorbing member I of the relay. For excluding as far as possibleforeign radiation a slit 35 is provided sufiiciently far in front of theopening 32, preferably in the form of the opening of a tube 34 attachedto the housing 3I over the opening 32, which is preferably also shapedas a slit cooperating with slit 35. If desired or found practical slit35 may be placed further away from opening 32, possibly in the formof aseparate slit screen. The slits are preferably rectangular having aheight about equal to the length of band I and a width not much greaterthan that of band I. By adequately spacing the slits relative to theirlengths and breadths the angular portion of the space in front of theslit 35 from which radiation can pass the slit arrangement and reach theband I may be suitably restricted.

In order that the relay shall obtain as much as possible of theradiation permitted by the slits the opening .3 2 may be quite'open andnot provided with a glass" window or the lik.' -iiiil'iis involves,however, a'certain disadvantage, inasmuch as dust andsoot and thelike'may enter the housing and pollute the bands of the relay.Therefore, according to a further embodimentef the invention ages inlet31 is provided for the admission of pressure air, preferably from thepressure air system of'the burne of aheat'er for which therelay maybearranged. A Special outlet'for the air may be provided but usually theopening @Iwilfdd with gr at sax/asses. since'therby the admittance ofpollutions will beprohibited ,7.

The device just described may readily be Slip-1 plemented sosimultaneously to be useful as an automaticair pressure indicator.Fofthis object inlet'31 rec nnected to'the'compressed air systemb'y tubeiiand' its interior projecting end is provided with afcove'r38 pivotedabout'a stub :33 mounted in a bracket 44. Secured to said cover isa'contact' arrhtill carrying a contact point 3| arranged to cooperatewith a stationary contact disc'z'conricted to the outer wire 43. Thecover is normally'urged against the opening of inlet 37 bya spring 46which is weak'enough to permit the pressure air stream passing throughthe inlet to lift the cover and bring about contact between contactpoint .4! and disc 42. electric conduit will be closed from wire 43through the detailsfl, 4!, 4G, 39 and I9 to the holder 4 of theradiation relay and, if therein the contact H3 44 is closedas explainedabove; fur ther to wire i8 and the outer Wire 48.

By this'arrangement the radiation relay and the air pressure indicatorare connected in series and if the wires 43 and 48 are connected to anelectric relay, not shown, for a signal device, such as a bell or lamp,or for means for cutting off the supply of fuel or the like, a signalwill be given, or the fuel supply be cut off, respectively, as soon asthe flame becomes extinguished or the air compressor or'pressure airsystem gets out of function.

Fig. 4 shows an oil heated furnace 5| equipped with a relay 31' of thepresent kind. From the oil burner 52 projects the flame 53. The radiation absorbing member of the relay 3! will be exposed to theradiationfrom the flame 53' through the relatively narrow channel 54 inthe wall of the furnace. The'chann'el 54 is preferably'di rectedagainsta' remote point 55 of the inside wall of the combustion room 55 so as tominimize the radiationfromdhe wall to the relay. At point 55 the wallmay be cooled or excavated so as to reduce the radiation from there; Inorder to increase the influence of the'radiation from the flame therelay is placed near the channel 55. Generally, the relay should be nearthe flame but far away from the wall 55.

Having now particularly described and ascertained the nature of my saidinvention and in What manner the same is to be performed, 1 declare thatwhat I claim is:

l. A radiation relay comprising an elongated radiation absorbingexpansion member, an clon gated temperature compensating expansionmemher, a support on which each of said members is mounted at one of theends thereof, a contact lever, said members being fixed to said lever atthe other ends thereof at spaced points on said lever, whereby saidmembers move said lever in the same direction as and by substan tiallythe same amount that said members expand Thereby due to variations inthe ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotatesaid'leverabout the point at which said temperaturecompensating member is fixed tosaid lever, a movable contact element mounted on one si'deof said leverwhich extends in a di rection substantially parallel to the direction inwhich said members expand, and a stationary contact element mounted at aposition opposite to said movable contact element, whereby said contactelements engage each other as a result of a given differential thermalexpansion of said mem er 2, A radiation relay comprising an elongatedradiation absorbing expansion member, an elonsated tempera u e c m n atxpa m ber, a support on which each of said members are mounted at one ofthe ends thereof, a contact lever. said members being fixed to saidlever at the other ends thereof at spaced points on said lever, wherebysaid members move said lever in the same direction as and bysubstantially the same amount that said members expand due to variationsin the ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotate said leverabout the point at which said temperature compensating member is fixedto said lever, a movable contact element mounted on one side of saidlever which extends in a direction substantially parallel to thedirection in which said mem bers expand, a stationary contact elementmounted at a position opposite to said movable contact element, wherebysaid contact elements engage each other as a result of a givendifferential thermal expansion of said members, and a projection portionon said lever, said portion extending in a direction parallel to thedirection of expansion of said members and having said movable contactelement mounted thereon.

3. A radiation relay comprising an elongated radiation absorbingexpansion member, an elongated temperature compensating expansionmember, a support on which each of said members are mounted at one ofthe ends thereof, a contact said members being fixed to said lever atthe other ends thereof at spaced points on said lever, whereby saidmembers move said lever in the same direction as and by substantiallythe same amount that said members expand due to variations in theambient temperature of said relay, and whereby said radiation absorbingmember upon absorbing radiation heatwill rotate said lever about thepoint at which said temperature compensating member is fixed to saidlever, a movable contact element mounted on one side of said lever whichextends in a direction substantially parallel to the direction in whichsaid members expand, a stationary contact element mounted at a positionopposite to said movable contact element, whereby said contact elementsengage each other as a result of a given differential thermal expansionof said members, anda'prqjection'portion on said lever, said portionextending in a direction parallel to and being located alongside of saidmembers and said portidn having said movable contact element mountedthereon.

A radiation relay comprising an elongated radiation absorbing expansionmember, an elona ed tem era compensa i exp s n em= per, a support on'which each of said members are mounted atone of the ends thereof, acontact lever, said members being fixed to said lever at the other endsthereof at spaced points on said lever, whereby said members move saidlever in the same direction as and by substantially the same amount thatsaid members expand due to variations in the ambient temperature of saidrelay, and whereby said radiation absorbing member upon absorbingradiation heat will rotate said lever about the point at which saidtemperature compensating member is fixed to said lever, a movablecontact element mounted on one side of said lever which extends in adirection substantiall parallel to the direction in which said membersexpand, and a stationary contact element mounted at a position oppositeto said movable contact element, whereby said contact elements engageeach other as a result of a given diiferential thermal expansion of saidmembers, the distance between said movable contact element and theextended line connecting said points at which the expansion members arefixed to said lever being greater than the distance between the pointsat which said members are fixed to said lever.

5. A radiation relay comprising an elongated radiation absorbingexpansion member, an elongated temperature compensating expansionmemher, a support on which each of said members are mounted at one ofthe ends thereof, a contact lever, said members being fixed to saidlever at a the other ends thereof at spaced points on said lever,whereby said members move said lever in the same direction as and bysubstantially the same amount that said members expand due to variationsin the ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotate said leverabout the point at which said temperature compensating member is fixedto said lever, a movable contact element mounted on one side of saidlever which extends in a direction substantially parallel to thedirection in which said members expand, and a stationary contact elementmounted at a position opposite to said movable contact element, wherebysaid contact element engage each other as a result of a givendifferential thermal expansion of said members, one of said contactelements having a contact surface which is arranged at a slight anglewith respect to the direction of thermal expansion of said members.

6. A radiation relay comprising an elongated radiation absorbingexpansion member, an elongated temperature compensating expansionmember, a support on which each of said members are mounted at one ofthe ends thereof, a contact lever, said members being fixed to saidlever at the other ends thereof at spaced points on said lever, wherebysaid members move said lever in the same direction as and bysubstantially the same amount that said members expand due to variationsin the ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotate said leverabout the point at which said temperature compensating member is fixedto said lever, a movable contact element mounted on one side of saidlever which extends in a direction substantially parallel to thedirection in which said members expand, and a stationary contact elementmounted at a position opposite to said movable contact element, wherebysaid contact elements engage each other as a result of a givendifferential thermal expansion of said members, said radiation absorbingmember being of a different length than said temperature compensatingmember.

'7. A radiation relay comprising an elongated radiation absorbingexpansion member, an elongated temperature compensating expansionmember, a support on which each of said members are mounted at one ofthe ends thereof, a contact lever, said members being fixed to saidlever at the other ends thereof at spaced points on said lever, wherebysaid members move said lever in the same direction as and bysubstantially the same amount that said members expand due to variationsin the ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotate said leverabout the point at which said temperature compensating member is fixedto said lever, a movable contact element mounted on one side of saidlever which extends in a direction substantially parallel to thedirection in which said members expand, and a stationary contact elementmounted at a position opposite to said movable contact element, wherebysaid contact elements engage each other as a result of a givendifierential thermal expansion of said members, said radiation absorbingmember having a coeflicient of thermal expansion different from that ofsaid temperature compensating member.

8. A radiation relay comprising an elongated radiation absorbingexpansion member, an elongated temperature compensating expansionmember, a support on which each of said members are mounted at one ofthe ends thereof, a contact lever, said members being fixed to saidlever at the other ends thereof at spaced points on said lever, wherebysaid members move said lever in the same direction as and bysubstantially the same amount that said members expand due to variationsin the ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotate said leverabout the point at which said temperature compensating member is fixedto said lever, a movable contact element mounted on one side of saidlever which extends in a direction substantially parallel to thedirection in which said members expand, and a stationary contact elementmounted at a position opposite to said movable contact element, wherebysaid contact elements engage each other as a result of a givendifferential thermal expansion of said members, said radiation absorbingmember having different surface areas than said temperature absorbingmember so that said temperature compensating member reacts more quicklyto changes in ambient temperature than said radiation absorbing member.

9. A radiation relay comprising an elongated radiation absorbingexpansion member, an elongated temperature compensating expansionmember, a support on which each of said members are mounted at one ofthe ends thereof, a contact lever, said members being fixed to saidlever at the other ends thereof at spaced points on said lever, wherebysaid members move said lever in the same direction as and bysubstantially the same amount that said members expand due to variationsin the ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotate said leverabout the point at which said temperature compensating member is fixedto said lever, a movable contact element mounted on one side of saidlever which extends in a direction substantially parallel to thedirection in which said members expand, and a stationary contact elementmounted at a position opposite to said movable contact element, wherebysaid contact elements engage each other as a result of a givendifferential thermal expansion of said members, the heat capacity ofsaid radiation absorbing member being difierent from that of saidtemperature compensating member so that one of said members reacts morequickly to changes in temperature than the other.

10. A radiation relay comprising an elongated radiation absorbingexpansion member, an elongated temperature compensating expansionmember, a support on which each of said members are mounted at one ofthe ends thereof, a contact lever, said members being fixed to saidlever at the other ends thereof at spaced points on said lever, wherebysaid members move said lever in the same direction as and bysubstantially the same amount that said members expand due to variationsin the ambient temperature of said relay, and whereby said radiationabsorbing member upon absorbing radiation heat will rotate said leverabout the point at which said temperature compensating member is fixedto said lever, a movable contact element mounted on one side of saidlever which extends in a direction substantially parallel to thedirection in which said members expand, and a stationary contact elementmounted at a position opposite to said movable contact element, wherebysaid contact elements engage each other as a result of a givendifferential thermal expansion of said members, said radiation absorbingmember having different cross sectional areas than said temperatureabsorbing member so that said temperature compensating member reactsmore quickly to changes in ambient temperature than said radiationabsorbing member.

11. A radiation relay, comprising in combination, a radiation absorbingexpansion member having a fixedly mounted portion and having a portionthereof freely movable in a predetermined direction upon expansion orcontraction of said radiation absorbing expansion member; a temperaturecompensating expansion member located adjacent to and spaced from saidradiation absorbing expansion member and also having a fixedly mountedportion and a portion freely movable in said predetermined direction; atwo-armed lever having the arms thereof located substantially at rightangles to each other, having one of the arms thereof extending along adirection substantially parallel to said predetermined direction andhaving the other arm thereof fixedly connected to said expansion membersat two spaced points of said other arm, respectively, so that when oneof said expansion members moves, due to expansion or contraction, withrespect to the other of said expansion members, said lever will bepivoted about the point thereof connected to said other expansionmember; a, first contact element mounted on said one arm of said leveradjacent the end thereof distant from said other arm of said lever; anda second contact element located opposite said first contact element, sothat said contact elements may engage each other as a result of a givendifferent thermal expansion of said members.

12. A radiation relay, comprising in combination, a dish-shapedradiation absorbing expansion member having a fixedly mounted peripheralportion so that the central portion thereof moves upon expansion orcontraction of said radiation absorbing expansion member; a dish-shapedtemperature compensating expansion member mounted coaxially with respectto said radiation absorbing expansion member and being spaced therefromand substantially parallel thereto, said temperature compensatingexpansion member also having a fixedly mounted peripheral portion sothat the central portion thereof moves upon expansion or contraction ofsaid radiation absorbing expansion member, the movement of said centralportions of said expansion members being in the same direction; atwo-armed lever having the arms thereof located substantially at rightangles to each other and having one arm thereof extending along a lineparallel to said direction and the other arm thereof located betweensaid expansion members and being fixedly connected to the same at twospaced points on said other arm of said lever, respectively, so thatwhen one of said expansion members moves with respect to the other ofsaid expansion members, said lever is pivoted about the point thereofconnected to said other of said expansion members; a first contactelement mounted adjacent an end of said one arm located distant fromsaid other arm of said lever; and a second contact element locatedopposite said first contact element, so that said contact elements mayengage each other as a result of a different given thermal expansion ofsaid members.

SVEN I-IARALD LEDIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

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